Analysis of stripline-fed slot-coupled patch antennas with vias for parallel-plate mode suppression

The paper presents an analysis of slot-coupled stripline-fed patch antennas with vias around the slot to minimize the power launched into the parallel-plate mode. A moment-method scattering formulation is invoked to include the effect of vias on the impedance characteristics of the antenna. Coupling between the stripline feed and the ground-plane slot is obtained by invoking reciprocity. Two design examples were fabricated and the measured input impedances verify the accuracy of the analysis. Vias considerably modify the impedance and resonant characteristics of a patch antenna. The radiation efficiency of patch antennas with and without vias is studied and proper location of the vias is shown to drastically reduce power in the parallel-plate mode.